Plasma-enhanced atomic layer deposition of tungsten diselenide thin films using bis( tert -butylimido)bis(dimethylamino)tungsten and H2Se plasma

Two-dimensional transition metal dichalcogenides are promising for next-generation technologies due to their unique optical and electronic properties. Tungsten diselenide (WSe2) is especially attractive because of its ambipolar conductivity and high theoretical carrier mobility. However, conventional high-temperature chemical vapor deposition limits WSe2 growth on 3D nanostructured or thermally sensitive substrates. Atomic layer deposition (ALD) could enable large-area, conformal WSe2 synthesis at back-end-of-line compatible temperatures, though it remains underexplored for this material. In this work, we develop and characterize a plasma-enhanced ALD process for 2D layered WSe2 using bis(tert-butylimido)bis(dimethylamino)tungsten as the precursor and pure H2Se plasma as the coreactant at 300 °C. Surface saturation conditions for the precursor and coreactant were established using atomic force microscopy. At 300 and 400 °C, a growth rate of ∼0.3 Å/ALD cycle was obtained. An 8-in wafer map of films deposited at 300 °C demonstrates high thickness uniformity and process scalability. 10 nm thick films grown at both 300 and 400 °C are characterized using Raman, grazing-incidence XRD, XPS, AFM, and SEM. As deposited, the films are crystalline, stoichiometric, and have rough surface morphologies. Cross-sectional STEM and energy-dispersive x-ray spectroscopy indicate crystalline 2D WSe2 layers that are aligned parallel to the surface. Some large amorphous tungsten selenide features are also present, likely caused by selenium contamination and related secondary-deposition processes in the reaction chamber.